The recent identification of the retrovirus HTLV III/LAV as the probable cause of AIDS has shifted our focus from the causative agent to its control, treatment and prevention. It is now important to define the early and late clinical, virologic, serologic and immunologic events associated with HTLV III/LAV infection. Questions to be answered include a knowledge of long term manifestations of infection with HTLV III/LAV prior to development of diagnosed AIDS and in patients who have antibody to the virus but have not developed defined AIDS or pre-AIDS. The intramural research contract with NYBC and Memorial Sloan-Kettering was designed to collect specimens in a prospective fashion from 325 homosexual males. Three populations were recruited: (l) patients with lymphadenopathy (l00), (2) normal plasma donors (175) and (3) normal homosexual males from a geographically distinct area in New York State (50). Specimens of peripheral blood leukocytes, plasma, serum, urine, saliva and stool are being collected at intervals along with epidemiological information. During the first year of the contract, five participants in group 1 or 2 have been diagnosed as having AIDS. We are currently awaiting the results of ELISA tests for antibody to HTLV III/LAV in the serum of participants from group 1, 2 and 3. Using these specimens collected over several years, it may be possible to correlate the presence of HTLV III/LAV antibody to clinical disease, to locate and isolate the virus from several sources and to gain information about changes in immune function in participants with antibody to HTLV III/LAV who do or do not develop AIDS.